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June 5, 1951 Patented June 5, 1951 MULTIVIBRATOR CIRCUIT Edmond Egbertus Carpentier, Eindhoven, Netherlands, assgnor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application May 4, 1946, Serial No. 667,253 In the Netherlands March 10, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires March 10, 1962 (Cl. Z50-36) 3 Claims.

This invention relates to a multivibrator circuit comprising two amplifying valves in which the circuit of an output electrode of each of the tubes is coupled via a condenser to the control grid circuit of the other tube and in which, as usual, the supply voltages of at least two similar output electrodes of the two tubes are obtained from a common source of anode voltage.

As is well-known, it is desirable that the steepness of the flank of the, say, pulse-shaped oscillations generated by means of the multivibrator circuit arrangement should be as large as possible.

The invention has for its object to provide im proved multivibrator circuit arrangements of the said type permitting of, say, pulse-shape oscillations having a particularly large flank steepness being obtained. l

According to the invention, a resistance is included in a common part of the supply circuit of two similar output electrodes of the two ampliiier valves.

The resistance included in the common part of the supply circuit is preferably about as heavy as the resistances included in the separate parts of this supply circuit.

'In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawing, in which the single ligure shows a preferred form of construction of the multivibrator circuit arrangement according to the invention.

The illustrated multivibrator circuit for generating pulse-shaped oscillations or else periodical voltages varying rectangularly with time comprises two pentodes I, 2 which disrupt each other alternately and whose cathodes 3, 4 are interconnected and connected to the earthed terminal 5 of an anode voltage battery 6. The screen grid 'l or 8 respectively of each of the tubes is connected on the one hand via a condenser I, 9 respectively to the control grid I2 or Il respectively and on the other hand via a resistor I3 or I4 respectively to the positive terminal 5 of the battery 6. The control grids II, I2 of the tubes I, 2 are connected to the cathode by resistances I5 and I6 respectively. The anode conductor of the tubes I, 2 which is connected to the terminal 5 of the battery includes anode resistances I'I, I3.

In the circuit arrangement shown the generated oscillations (20) may be obtained from the output terminals I9. For this purpose, the output terminals are connected respectively via block connection between the anode resistances I'I, I8

have interconnected between them a resistance 25, 25 a preferably adjustable tapping point 26 of which is connected directly to the positive terminal 5 of the battery 6. The parts 25 and 25 of this resistance, which are located on either side of the tapping point, are thus included each in a common part of the screen grid and of the anode circuits of the tubes I, 2.

Each of the resistances 25 and 25 common respectively to the anode and the screen grid circuits respectively of the tubes l, 2 supports by itself the coupling brought about between the tubes I and 2 by the condenser-resistance combination 9, I5 and I, i6 respectively, as will be set out more fully hereinafter. This inter alia renders possible a greater liberty as regards the choice of the dimensions of the other elements of the circuit, particularly of the condenser-resistance combination 9, I5 and lil, I6 respectively, with the result that the possibilities of using' circuit arrangements of the present kind are extended.

The operation of the circuit illustrated is as follows.

If at a given moment the tube I is just disrupted and the tube 2 just has an electric current passing through it, the potential of 'the control grid II of the tube l will be increased to such extent after a lapse of a period governed by the condenser resistance 9, I5, that the disruption of the tube I is suppressed and thus a low current again starts to flow through the tube. As a result of the voltage drop consequent upon the occurrence of a screen-grid current at the screen grid resistance I3 and the resistance 2e' the potential of the screen grid I and-since the voltage at the condenser Il! cannot change immediately-also the potential of the control grid l2 of the tube 2 falls. At the same time, however, the `potential of the screen grid 8 of the tube 2 is decreased by the larger voltage drop that occurs at the resistance 25 which is common to the 3 twoscreening grid circuits. The current passing through the tube '2 then decreases due on the one hand to the decrease in potential at the 4control grid l2 and due on the other hand to the decrease in potential of the screen grid. The

disruption of the tube 2 is therefore assisted by The measure according to the invention also enables the condenser resistance combination 9, I5 and I0, I6 to be proportioned in such manner that these alternating voltages which by themselves bring about a coupling insufficient for generating alternating voltages which practically vary with time rectangularly, as may be desirable for example for obtaining a small RC-time for generating pulse-shaped oscillations of high frequency or in the case theoutput voltages are derived from resistances included in the respective cathode leads of the tubes bringing about negative feedback coupling; for bringing about in these cases a coupling which nevertheless is suiciently strong may be obtained by the provision of resistances common to the supply circuits of the two tubes.

It has been found favourable to choose the re sistances 25 and 25 respectively in such manner that the value corresponds approximately to the value of each of the anode resistances l1, i8 or screening-grid resistances I3, i4 respectively.

It may be mentioned that the invention can also evidently be used with multivibrator circuit arrangements in which instead of pentodesuse may be inade of tubes of another type, for example triodes.

I claim:

1. A high-frequency multivibrator circuit comprising first and second electron discharge de- `vices each having a cathode, a control grid, a

screen grid and an anode, rst and second resistances having the same predetermined value and serially connected between the anodes of said devices, third and fourth resistances having the same predetermined value and serially connected between the screen grids of said devices, means capacitatively coupling the screen grid of said first device to the control grid of said second device, means capacitatively coupling the screen grid of said second device to the control grid of said first device, a resistance element havingY an adjustable tap and connected between the junction of said serially connected rst and second resistance and the junction of said serially connected third and fourth resistances, and a common source of constant potential for said devices connected between the cathodes thereof and the tap in said element.

2. A high-frequency multivibrator circuit comprising rst and second electron discharge devices each having a cathode, a control grid, a

screen grid and an anode, rst and second resistances having the same predetermined value and serially connected between the anodes cf said devices, third and fourth resistances having the same predetermined value and serially connected between the screen gridsof said devices, means capacitatively coupling the screen grid of said iirst device to the control grid of said second device, means capacitatively coupling the screen grid of said second device to the control grid of said rst device, a fth resistance having a value substantially equal to the respective values of said rst and second resistances, a sixth resistance having a value substantially equal to the value of said third and fourth resistances, and a common source of constant potential for said devices having one terminal connected to the cathodes thereof and the other terminal connected through said iifth resistance to the junction of said serially connected first and second resistances and through said sixth resistance to the junction of said serially connected third and fourth resistances.

3. A high-frequency multivibrator circuit cornprising iirst and second electron discharge devices each having a cathode, a control grid, a screen grid and an anode, first and second resistances having the same predetermined value and serially connected between the anodes of said.

devices, third and fourth resistances having the same predetermined value and serially connected between the screen grids of said devices, a rst capacitor having a relatively small value connecting the screen grid of the first device to the control grid of the second device, a second capacitor having a relatively small value connecting the screen grid of the second device to the control grid of the first device, a fth resistance having a value substantially equal to the respective values of said first and second resistances, a sixth resistance having a value substantially equal to the respective values of said third and fourth resistances, a common source of constant potential'for said devices having one terminal connected to the cathodes thereof and the other terminal connected through said fifth resistance to the junction of said serially connected first and second resistances and through said sixth resistance to the junction of said serially connected third and fourth resistances, a pair of output terminals, a third capacitor connecting the anode of said rst device to one of said output terminals, and a fourth capacitor connecting the anode of said second device to the other of said Youtput terminals. i

EDMOND EGBERTUS CARPENTIER.

REFERENCES CITED 

